Asthma and chronic obstructive lung disease (COPD) are some of the leading causes of morbidity in children and adults, respectively. Asthma is the most common chronic disease of childhood in the developed world, incurs significant healthcare costs, and the prevalence of asthma has continued to increase. It has been estimated that as many as 16 million Americans have COPD and it is now the fourth most common cause of death in the United States. Among the top 5 causes of death, COPD is the only major disease that is continuing to increase in both prevalence and mortality. There is preliminary data that vitamin D intake can affect the development of wheezing phenotypes in young children and that serum vitamin D levels are associated with lung function. Vitamin D receptors are present in immune cells and vitamin D plays a role in the development and function of the cells of the immune system, and it is postulated that vitamin D may play a role in asthma and COPD via these effects on the immune system. However, there have been no studies that have shown decreased vitamin D levels in subjects with asthma or COPD. Thus, before pursuing more expensive and definitive studies such as clinical trials of vitamin D supplementation, more convincing evidence is needed for the association between vitamin D and these lung diseases. This project proposes to measure vitamin D levels from stored serum samples in three cohorts - two asthma cohorts (the Childhood Asthma Management Program cohort and the Genetics of Asthma in Costa Rica cohort) and an adult general population cohort (the Normative Aging Study cohort). We will determine whether there are any differences in vitamin D levels between Caucasian, African- American, and Hispanic asthmatics, and whether vitamin D is associated with more severe asthma in the asthma cohorts. We will also determine whether vitamin D is associated with lung function decline and development of COPD in the adult cohort. If we are able to demonstrate an association between vitamin D and these outcomes, this will pave the way for more definitive studies of the role of vitamin D in obstructive lung diseases, asthma and COPD. Showing a relationship between vitamin D levels in serum and obstructive lung diseases will have great public health significance and will add to the evidence that recommended vitamin D intakes need to be increased. Additionally, supplementation with vitamin D can be implemented in cost-effective population-based programs to prevent the development of, and treat these disorders. [unreadable] [unreadable] [unreadable]